PURPOSE: To facilitate positioning of scrolls by a method wherein, in a scroll fluid machine having two scrolls driven with the aid of respective motors, a first scroll is positioned from the number of rotation output pulses when the first scroll is rotated by constraining a second scroll.

CONSTITUTION: In a scroll fluid machine having first and second scrolls 7 and 11 rotated with the aid of motors 8 and 12, respectively, during setting of an initial position, rotation of the second scroll 11 is first constrained by a mechanical means. After the first scroll 7 is moved in the direction of an arrow mark 37 to bring it into contact (at a contact point 38a) with the second scroll 11, the first scroll 7 is rotated in the direction of an arrow mark 40 to bring it into contact (at a contact point 38b) with the second scroll 11, and the current number of output pulses is read by a counter 33. The above control is effected in a plurality of spots in an axial direction, and a relative position between the two scrolls 7 and 11 at a period responding to the minimum number of output pulses of the number of output pulses in each position is positioned as an approximately regular relative position.